JP5561150B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 discloses an example of a conventional image forming apparatus. The image forming apparatus includes an apparatus main body provided with a conveyance path through which a recording medium is conveyed, an endless belt that constitutes a part of the conveyance path and circulates while conveying the recording medium, and above the endless belt. And a plurality of process cartridges respectively containing a plurality of colors of toner. Each process cartridge has an image carrier on which an electrostatic latent image is formed, and a developing unit that supplies toner to the image carrier and visualizes the electrostatic latent image, along the conveyance path. Side by side, images of a plurality of colors are sequentially stacked on the recording medium.

  Further, the image forming apparatus has a detection surface facing the endless belt, reads a detection pattern formed by each process cartridge on the endless belt through the detection surface, and a reading result of the reading unit. And detecting means for detecting a positional deviation between the images formed by the process cartridges.

  In the image forming apparatus having the above-described configuration, the detection unit detects the positional deviation between the images formed by the process cartridges based on the result of the reading unit reading the detection pattern on the endless belt during color image formation. Then, correction is performed so that the images overlap correctly.

  Here, if dirt such as toner or dust adheres to the detection surface, it becomes difficult to maintain the detection accuracy of the reading unit, and it becomes difficult to prevent positional deviation between the images. For this reason, in this type of image forming apparatus, for example, a configuration in which the user manually cleans the detection surface to remove the stain, or a shutter member that covers the detection surface is provided so that the detection surface is stained. The detection accuracy of the reading means is maintained by adopting a configuration for preventing the above.

JP 10-115962 A

  However, in the above-described conventional image forming apparatus, when the user manually cleans the detection surface, the cleaning frequency varies. Therefore, it is difficult to reliably maintain the detection accuracy of the reading unit, and the positional deviation between the images can be reliably ensured. Difficult to prevent. In addition, when a shutter member that covers the detection surface is provided, an open / close switching mechanism for automatically opening and closing the shutter member is required, and there is a problem that the configuration of the apparatus is likely to be complicated.

  The present invention has been made in view of the above-described conventional situation, and provides an image forming apparatus capable of reliably preventing positional deviation between images during color image formation while realizing simplification of the apparatus configuration. For the purpose.

An image forming apparatus of the present invention includes an apparatus main body provided with a conveyance path through which a recording medium is conveyed,
An endless belt that circulates in contact with the recording medium transported along the transport path;
An image carrier on which an electrostatic latent image is formed, and a developing unit that supplies toner to the image carrier and visualizes the electrostatic latent image, and circulates above the endless belt. A plurality of process cartridges that are arranged along a direction and sequentially form a plurality of color images on the recording medium or the endless belt;
An image forming apparatus comprising: a displacement unit that switches the process cartridge between a first state in which image formation is possible and a second state in which image formation is impossible by relative displacement with respect to each process cartridge;
A reading unit having a detection surface facing the endless belt, and reading a detection pattern formed on the endless belt by the process cartridges to detect a positional shift between the images through the detection surface; ,
Detection means for detecting a positional deviation between the images formed by the process cartridges based on a reading result of the reading means;
A shutter member provided between the endless belt and the detection surface and capable of being displaced to a closed position covering the detection surface and an open position opening the detection surface;
In conjunction with the relative displacement of the displacement means with respect to each process cartridge, the shutter member is displaced to the closed position when the reading means does not operate, while the shutter member is moved when the reading means operates. An interlocking mechanism for displacing to the open position ,
The displacement means can be displaced between a first range and a second range in a state where a plurality of the process cartridges are switched to the first state, and in the first range, the shutter member is displaced to the closed position. are allowed, in the second range, you characterized that you have configured the shutter member to displace said open position.

  According to the image forming apparatus of the present invention, the interlocking mechanism displaces the shutter member in conjunction with the displacement of the displacement means that switches each process cartridge to the first state or the second state. At this time, the interlocking mechanism displaces the shutter member to the closed position when the reading unit does not operate, and displaces the shutter member to the open position when the reading unit operates. For this reason, since the shutter member covers the detection surface during a period when the detection means is not used, it is possible to reliably prevent adhesion of dirt such as toner and dust to the detection surface. As a result, since this image forming apparatus can reliably maintain the detection accuracy of the reading unit, it is possible to reliably prevent misalignment between the images during color image formation.

  In addition, since the shutter member is opened and closed by the displacing means and the interlocking mechanism, it is not necessary to provide an opening / closing switching mechanism dedicated to the shutter member, so that the apparatus configuration can be simplified.

Therefore, the image forming apparatus of the present invention can reliably prevent the positional deviation between the images when forming a color image while realizing simplification of the apparatus configuration.
The interlocking mechanism is preferably configured to displace the shutter member to the open position when the displacement means switches the plurality of process cartridges to the first state for color image formation. According to this configuration, the interlocking mechanism reliably displaces the shutter member to the open position during color image formation, which is the case where the reading unit operates. For this reason, it is possible to reliably perform a misalignment detection operation between the images when forming a color image.
In the image forming apparatus of the present invention, the displacement means can be displaced between the first range and the second range in a state where the plurality of process cartridges are switched to the first state. The displacement means is configured to displace the shutter member to the closed position in the first range, and to displace the shutter member to the open position in the second range. In the case of color image formation, each process cartridge forms a detection pattern on the endless belt in a period different from the period in which the image is formed on the recording medium, and the reading unit reads the detection pattern. Then, based on the reading result of the reading means, the detection means detects the positional deviation between the images formed by the process cartridges, and the positional deviation detection work is completed. After the misregistration detection operation is completed, misregistration adjustment processing and the like are performed, and a color image is actually formed on the recording medium. For this reason, according to the above configuration, after the reading unit and the detecting unit perform the displacement detection operation in a state where the moving unit is displaced to the second range and the shutter member is moved to the open position, Displacement within one range and displacement of the shutter member to the closed position can reliably prevent dirt from adhering to the detection surface during color image formation after completion of the misalignment detection operation, which is a case where the reading unit does not operate. . As a result, it becomes easier to maintain the detection accuracy of the reading means, and the positional deviation between the images can be more reliably prevented.

The displacing means has a main body portion that is relatively displaced along the arrangement direction of the process cartridges, and a plurality of action portions that are provided at positions corresponding to the process cartridges in the main body portion and that are displaced integrally with the main body portion. Is desirable. When the main body portion is relatively displaced in the forward direction or the reverse direction with respect to each process cartridge, the developing unit is brought into contact with or separated from the image carrier in the process cartridge corresponding to the operation unit, and the corresponding process cartridge is moved to the first position. it is not to demand that is configured to switch to one state or the second state. According to this structure, simplification of an apparatus structure is reliably realizable by the simple displacement means which has a main-body part and an action part.

The main body is an extending member that extends from the process cartridge on one end side in the arrangement direction to the process cartridge on the other end side, and each action portion is a cam that protrudes from the main body toward the corresponding process cartridge. It is desirable. In addition, each process cartridge is preferably formed with an actuated portion that is connected to the developing unit and receives the action of the corresponding acting portion. By the actuated portion is guided to the working portion, not to want to be composed into contact with or separated from the developing unit to the image bearing member. According to this configuration, the main body portion (extending member) and the action portion (projected cam) constituting the displacement means function as a linear cam that moves in a direction along the alignment direction of the process cartridges. The device structure can be simplified more reliably by the direct acting cam and the actuated portion.

The interlocking mechanism is configured to displace the shutter member to the closed position when the displacement unit switches the remaining process cartridges to the second state while keeping one process cartridge in the first state for monochrome image formation. it is not the desirable you are. When forming a monochrome image, it is not necessary to detect misalignment between the images. For this reason, according to the above configuration, when the monochrome image is formed, which is a case where the reading unit does not operate, the interlocking mechanism displaces the shutter member to the closed position, so that it is possible to reliably prevent the dirt from adhering to the detection surface. As a result, it becomes easier to maintain the detection accuracy of the reading means, and the positional deviation between the images can be more reliably prevented.

The shutter member may have to desirable and a cleaning member for cleaning in contact with the detection surface when displaced to the closed position or open position. According to this configuration, when the shutter member is displaced, the cleaning member comes into contact with the detection surface of the reading unit, so that dirt attached to the detection surface can be removed, so that the detection surface can be easily maintained in a clean state. As a result, it becomes easier to maintain the detection accuracy of the reading means, and the positional deviation between the images can be more reliably prevented.

Interlocking mechanism, it has to desirable are disposed outward in the width direction of the endless belt. According to this configuration, since the interlocking mechanism is on the outer side in the width direction of the endless belt, interference between the other member disposed on the endless belt and the interlocking mechanism is less likely to occur. As a result, the interlocking mechanism can be operated reliably.

It is a schematic sectional drawing of the image forming apparatus of an Example. FIG. 6 is a perspective view showing a state in which one developing unit is attached to the drawer. FIG. 6 is a perspective view showing a state where one developing unit is removed from the drawer. It is a principal part perspective view which shows the displacement means and to-be-acted part when all the process cartridges are in a 1st state. (A) is a schematic side view showing a relative positional relationship among the action part, the acted part, the developing unit, and the image carrier when the process cartridge is in the first state, and (b) is a diagram illustrating the process cartridge. FIG. 6 is a schematic side view showing a relative positional relationship among an action part, an action part, a development unit, and an image carrier in a second state. It is a perspective view which extracts and shows a displacement means. It is a principal part perspective view which shows the displacement means and to-be-acted part in case process cartridges other than black are in a 2nd state. (A) is a principal part perspective view which shows the shutter member displaced to the closed position, the reading means, and the interlocking mechanism, and (b) is the shutter member displaced to the open position, the reading means, and the interlocking mechanism. It is a principal part perspective view which shows these. It is a principal part top view explaining the relative positional relationship of a detection pattern and a reading means. It is a schematic diagram explaining the cooperation operation | movement of a displacement means, a process cartridge, an interlocking mechanism, and a shutter member (The case where all the process cartridges are in a 1st state and a displacement means is in a 2nd range is shown.). It is a schematic diagram explaining the cooperation operation | movement of a displacement means, a process cartridge, an interlocking mechanism, and a shutter member (The case where all the process cartridges are in a 1st state and a displacement means is in a 1st range is shown.). It is a schematic diagram explaining the cooperation operation | movement of a displacement means, a process cartridge, an interlocking mechanism, and a shutter member (The case where process cartridges other than black are in a 2nd state is shown).

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

(Example)
As shown in FIG. 1, a printer 1 as an example of an image forming apparatus according to an embodiment is a color laser printer that forms a color image on a sheet (including an OHP sheet) as a recording medium by an electrophotographic method. . In FIG. 1, the right side of the sheet is defined as the front side of the apparatus, and the side that comes to the left hand (the front side of the sheet) when the apparatus is viewed from the front side is defined as the left side. 2 are displayed in correspondence with the directions shown in FIG. 1. Hereinafter, each component provided in the printer 1 will be described with reference to FIG.

1. Schematic Configuration As shown in FIG. 1, the housing 2 is a substantially box-shaped body, and a frame member is provided inside thereof. FIG. 4 shows the right main body side plate 81 constituting the frame member. A paper feeding unit 220, an image forming unit 10, a transport unit 11, a fixing device 13, and the like are assembled to the frame member. The housing 2 and the frame member constitute the apparatus main body of the present invention.

  Further, in the housing 2, a linear cam 92, a reading unit 300, a detecting unit 390, a shutter member 350, and an interlocking mechanism 400, which will be described in detail later, are provided. Further, a control unit (not shown) is provided in the housing 2 to control each of the above components so as to operate in cooperation with each other.

  On the upper surface of the housing 2, a discharge tray 14 for discharging the paper on which image formation has been completed is provided. In the housing 2, a substantially “S” -shaped path from the lower sheet feeding unit 220 to the upper discharge tray 14 via the image forming unit 10, the conveyance unit 11, the fixing device 13, and the like is a sheet conveyance path P. It is. A front cover 3 that can be opened and closed is provided on the front surface of the housing 2 with the lower end side as a swing center axis.

2. Paper Feed Unit The paper feed unit 220 feeds sheets stored in a paper feed tray 221 provided below the housing 2 to the transport path P one by one by a paper feed roller 222 and a separation pad 223. Then, the sheet is conveyed toward the image forming unit 10 by the conveyance rollers 224 and 225 and the registration rollers 226 and 227 disposed in a portion that is turned backward in a substantially U shape of the conveyance path P.

3. Transport Unit The transport unit 11 is disposed between the paper feed tray 221 and the image forming unit 10 and includes a transport belt 11C, four transfer rollers 12, and the like. The conveyor belt 11C is an example of an endless belt of the present invention.

  The conveyor belt 11C is wound around a driving roller 11A and a driven roller 11B that are positioned below the rear end side and below the front end side of the image forming unit 10. Then, the driving roller 11A rotates in synchronization with the paper feeding unit 220, whereby the conveying belt 11C circulates between the driving roller 11A and the driven roller 11B. The upper surface of the conveyance belt 11C extends substantially horizontally immediately below the image forming unit 10, contacts the back surface of the sheet, and follows the straight line portion that continues from the substantially U-shaped portion of the conveyance path P. The sheet conveyance surface 11D is conveyed.

  Each transfer roller 12 is provided in the transport unit 11 in a state of being in contact with the transport belt 11C from the back surface side of the sheet transport surface 11D. The conveyance belt 11C made of conductive rubber is negatively charged when a transfer voltage is applied to each transfer roller 12, and conveys the sheet along the conveyance path P while adsorbing the sheet to the sheet conveyance surface 11D by the electrostatic force. .

4). Image Forming Unit The image forming unit 10 includes a scanner unit 9 and four process cartridges 7. Each process cartridge 7 includes a photosensitive drum 5 that faces the transfer roller 12 with the paper transport surface 11D interposed therebetween, and a developing unit 8 that is positioned obliquely above the photosensitive drum 5. The photosensitive drum 5 is an example of the image carrier of the present invention.

  The scanner unit 9 is positioned at the top of the housing 2 and includes a laser light source, a polygon mirror, an fθ lens, a reflecting mirror, and the like. Then, the laser beam emitted from the laser light source is deflected by the polygon mirror, passes through the fθ lens, and then the optical path is folded by the reflecting mirror, and further, the optical path is bent downward by the reflecting mirror. Irradiated onto the surface of the photosensitive drum 5, an electrostatic latent image corresponding to four colors of black, yellow, magenta, and cyan is formed.

  Each process cartridge 7 corresponds to four colors of black, yellow, magenta, and cyan. The process cartridge 7 is below the scanner unit 9 and above the paper transport surface 11D from the upstream to the downstream in the transport direction of the paper transport surface 11D. They are arranged in series. In other words, the process cartridges 7 are arranged along the circulation direction of the transport belt 11C. The black process cartridge 7 is located at the forefront. As described above, a configuration in which the process cartridges 7 are arranged in series along the transport direction within a predetermined range in the paper transport path P is referred to as a “tandem type”.

  Each of the photosensitive drums 5 has a positively chargeable photosensitive layer formed on the outermost layer of a resin cylinder (the drum body 47 shown in FIG. 2 and the like). A known charger 6 is disposed in the vicinity of each photosensitive drum 5 so as to face the photosensitive layer of the photosensitive drum 5.

  Each developing unit 8 is provided in a box-shaped developing frame 51 having an opening at the lower rear side, an upper portion inside the developing frame 51, a toner containing chamber 7A for containing toner, and a supply provided below the developing frame 51. The roller 7B and the developing roller 7C exposed from the opening of the developing frame 51 and facing the photosensitive drum 5 are provided. The toner in the toner storage chamber 7A is supplied to the developing roller 7C side by the rotation of the supply roller 7B, is carried on the surface of the developing roller 7C, and is adjusted to a predetermined thickness by the layer thickness regulating blade 7D. It is supplied to the surface of the photosensitive drum 5.

5. Fixing Device The fixing device 13 is positioned downstream of the image forming unit 10 in the transport direction in the paper transport path P, and includes a heating roller 13A and a pressure roller 13B. The heating roller 13A rotates in synchronization with the conveyance belt 11C and the like, and applies a conveyance force to the sheet while heating the toner transferred to the sheet. On the other hand, the pressure roller 13B is driven to rotate while pressing the sheet toward the heating roller 13A. As a result, the fixing device 13 heats and melts the toner transferred onto the sheet to fix it on the sheet, and conveys the sheet to the downstream side of the conveyance path P. The conveyance path P is curved in a substantially U shape upward on the downstream side of the fixing device 13. The discharge rollers 228 and 229 and the discharge tray 14 are located on the most downstream side in the transport direction of the transport path P.

6). Outline of Image Forming Operation During image formation, the control unit starts control of the paper feeding unit 220, the image forming unit 10, the transport unit 11, the fixing device 13, and the like. Note that switching between color image formation and motocro image formation, and the misalignment detection operation between the images during color image formation will be described later.

  Under the control of the control unit, the paper feeding unit 220 and the transport unit 11 are operated to transport the paper to the image forming unit 10, and the scanner unit 9, each process cartridge 7 and the like are operated. Then, the surface of each rotating photosensitive drum 5 is uniformly positively charged by the charger 6 and then exposed to a laser beam emitted from the scanner unit 9 to form an image on the surface of each photosensitive drum 5. An electrostatic latent image corresponding to the data is formed.

  On the other hand, the positively charged toner carried on the developing roller 7 </ b> C rotates on the surface of each photosensitive drum 5 when the developing roller 7 </ b> C rotates while being in contact with each photosensitive drum 5. It is supplied to the formed electrostatic latent image. As a result, the electrostatic latent image on each photoconductive drum 5 is visualized, and a toner image by reversal development is carried on the surface of each photoconductive drum 5.

  Thereafter, the toner image carried on the surface of each photoconductor drum 5 is transferred onto a sheet by a transfer voltage applied to each transfer roller 12. When the sheet on which the toner image is transferred is conveyed to the fixing device 13, it is heated and pressed by the heating roller 13A and the pressing roller 13B, and the toner image is fixed on the sheet. Finally, the sheet on which the image is formed is discharged to the discharge tray 14 and the image forming operation is finished.

7). Drawer As shown in FIG. 1, in each process cartridge 7, in order to facilitate maintenance and replacement of consumables, as will be described in detail below, each photosensitive drum 5 is held by a drawer-4, The developing unit 8 is detachably held with respect to the drawer-4. The drawer 4 is pulled out from the position shown in FIG. 1 in the housing 2 with the front cover 3 opened, or inserted toward the back in the housing 2 from the front. The printer 1 can be attached to and pulled out from the apparatus main body. By pulling out the drawer 4, the developing unit 8 can be replaced. Further, the drawer 4 can be removed from the apparatus main body in a state where the drawer 4 is pulled out to the outside of the housing 2.

  As shown in FIGS. 2 and 3, the drawer 4 as a single unit includes a front front beam 21, a rear rear beam 22, and four intermediate beams 20 arranged in the front-rear direction between the front beam 21 and the rear beam 22. A pair of first side plates 23 (see FIG. 4) that extend in the front-rear direction and face each other in the width direction (the same direction as the left-right direction shown in each figure), and outward in the width direction of each first side plate 23 A pair of attached second side plates 24 are integrally assembled.

  The front beam 21 is installed between the front end portions of the pair of first side plates 23. The front beam 21 holds a support shaft 25. The support shaft 25 is disposed so as to penetrate the front beam 21 along the width direction, protrudes outward in the width direction from the front beam 21, and further includes a support shaft insertion hole 30 (see FIG. 4) of the first side plate 23 and the first. It penetrates through the support shaft insertion hole 35 (see FIG. 2) of the second side plate 24 and protrudes outward in the width direction. In the center of the front beam 21 in the width direction, a front side gripping portion 26 that protrudes upward is provided.

  The rear beam 22 is installed between the rear end portions of the pair of first side plates 23. At the center of the rear beam 22 in the width direction, a back side grip portion 27 that protrudes obliquely upward from the rear is provided. The front side gripping part 26 and the back side gripping part 27 are gripped by the user when the drawer 4 is attached or detached.

  The four intermediate beams 20 are installed between the pair of first side plates 23 with an interval in the front-rear direction. Each intermediate beam 20 is elongated in the width direction, and is formed in a substantially triangular prism shape with the lower front side open. Each intermediate beam 20 holds a charger 6 (see FIG. 1) and a cleaning member (not shown) for cleaning the surface of the photosensitive drum 5.

  FIG. 4 shows a view of the right first side plate 23 as viewed from the left. In the present embodiment, the left and right first side plates 23 are produced in the same shape by pressing a metal plate using the same press mold. The first side plate 23 is formed in a substantially elongated rectangular plate shape extending in the front-rear direction. Although not shown, the front end portion and the rear end portion of each first side plate 23 face each other so as to sandwich the front beam 21 and the rear beam 22 from the outside in the width direction.

  On the rear end side of the first side plate 23, an inclined portion extending obliquely upward in the rear direction and a linear portion extending substantially upward from the rear end of the inclined portion are formed. A cutout portion 31 having a substantially V-shaped cutout is formed near the boundary between the inclined portion and the straight portion. The first side plate 23 is formed with four circular drum support holes 32 arranged in the front-rear direction.

  As shown in FIGS. 2 and 3, a pair of second side plates 24 are provided on the left and right. Compared with the first side plate 23 (see FIG. 4), it is formed in a substantially elongated rectangular plate shape in side view having a width that is wide in the vertical direction and substantially the same length in the front-rear direction. The front end portion and the rear end portion of the second side plate 24 oppose each other so as to sandwich the front beam 21 and the rear beam 22 from the outside in the width direction through the first side plate 23, respectively.

  On the upper end portion of the second side plate 24, a flange portion 33 extending outward in the width direction is formed across the front-rear direction. An inclined surface 34 is formed at the front end portion of the flange portion 33 so as to incline from the lower surface toward the front upper side.

  The rear end portion of the second side plate 24 and below the flange portion 33 is formed narrower in the vertical direction than the front side of the second side plate 24. Specifically, the lower end edge of the second side plate 24 is inclined so as to face upward as it goes rearward. At the rear end portion of the second side plate 24, a notch portion 36 having substantially the same shape as the notch portion 31 is formed at a position facing the notch portion 31 (see FIG. 4) of the first side plate 23 in the width direction. .

  FIG. 4 shows the right side plate 24 as viewed from the left. On the surface facing the inner side in the width direction of the second side plate 24, there are four development unit guide portions 37 for guiding the attachment and detachment of the development unit 8 between the left and right second side plates 24 (see FIGS. 2 and 3). Are formed at regular intervals. The developing unit guide portion 37 is formed of two protrusions that protrude from the inner side surface of the second side plate 24 toward the inner side in the width direction and are spaced from each other. The developing unit guide 37 is inclined with a constant gradient from the upper end of the second side plate 24 obliquely downward in the rearward direction, and is connected to the developing unit holding unit 38. The developing unit holding part 38 is formed in parallel to a straight line H (see FIG. 1) connecting the center of the photosensitive drum 5 and the center of the developing roller 7C, and its lower end is opened toward the photosensitive drum 5.

  As shown in FIGS. 3 and 4, four second support shafts 39 that support a pressing cam 76, which will be described later, are swingably spaced from each other in the front-rear direction at the upper end portion of the inner surface of the second side plate 24. It is protruding from the sky. As shown in FIG. 3, four contact grooves 50 are formed in the upper end portion of the inner side surface of the second side plate 24 at regular intervals in the front-rear direction. FIG. 5A shows the relative positional relationship between the second support shaft 39, the contact groove 50, and the developing unit holding portion 38 when the developing unit 8 attached to the drawer 4 is viewed from the width direction.

  As shown in FIGS. 2 and 3, the left second side plate 24 has four drum coupling insertion holes 40 that expose the left end in the axial direction of each photosensitive drum 5 arranged at regular intervals in the front-rear direction. Is formed. The drum coupling insertion hole 40 extends the second side plate 24 in the thickness direction at a position facing the drum support hole 32 provided in the left end portion in the axial direction of each photosensitive drum 5 and the first side plate 23 on the right side in the width direction. It is formed as a round hole that penetrates. The left second side plate 24 is also formed with a developing unit guide portion 37 at a position facing each developing unit guide portion 37 of the right second side plate 24. A developing coupling insertion hole 41 is formed in the middle of each developing unit guide portion 37 in the vertical direction. As shown in FIG. 2, with each developing unit 8 mounted between the left and right second side plates 24, the developing coupling 64 provided on the left side surface of the developing unit 8 is inserted into each developing coupling insertion hole 41. Opposite.

  Although not shown, the second side plate 24 on the right side is provided with a plurality of electrodes. These electrodes are a plurality of spring-like electrodes that protrude from the inner side surface in the width direction of the right main body side plate 81 toward the second right side plate 24 facing the drawer 4 with being attached to the apparatus main body. , The power supply provided in the apparatus main body is electrically connected to the developing unit 8, the charger 6, and the like.

  As shown in FIGS. 2 and 3, the photosensitive drum 5 has two flange members 48 that are fitted to both ends of a cylindrical drum main body 47 so as not to be relatively rotatable. The left and right flange members 48 are rotatably supported with respect to the drum support holes 32 (see FIG. 4) of the left and right first side plates 23 by bearing members (not shown). A coupling groove 49 (see FIG. 3) for rotating the photosensitive drum 5 is provided on the left end surface of the left flange member 48 in combination with a drive transmission unit (not shown) provided in the housing 2. It has been.

  As shown in FIGS. 3 and 5A, the developing frame 51 has a pair of left and right side walls 55, and a front wall 56, a rear wall 57, and an upper wall 58 that connect the pair of side walls 55. Yes. Both end portions in the axial direction of the roller shaft 59 of the developing roller 7C penetrate the lower end portion of the side wall 55 and protrude outward in the width direction.

  A support shaft 60 is provided at a position above the front side of each side wall 55. The support shaft 60 protrudes from the side wall 55 toward the outside in the width direction. A moving member 61 is swingably supported on the support shaft 60. The moving member 61 is an example of the operated part of the present invention.

  A columnar development pressing boss 62 projects from the side wall 55 outward in the width direction at a position above the support shaft 60 in the front side. Further, a spring (not shown) is provided around the support shaft 60, and the moving member 61 is biased counterclockwise in FIG. 5A by the biasing force of the spring.

  As shown in FIG. 3, a restricting boss 63 for restricting the swing range of the moving member 61 protrudes from the side wall 55 outward in the width direction above the support shaft 60. On the left side wall 55, a development coupling 64 is disposed at a position above the front side with respect to the roller shaft 59. The developing coupling 64 is connected to a plurality of gears (not shown) for transmitting a rotational driving force to the developing roller 7C and the supply roller 7B (see FIG. 1).

  As shown in FIGS. 3 and 5A, a pair of moving members 61 are provided on both sides in the width direction of the developing unit 8, and a main body 70 extending in a direction orthogonal to the axial direction of the support shaft 60 is provided. Have. One end of the main body 70 forms a connecting portion 71 that is rotatably supported by the support shaft 60. The other end portion of the main body 70 is bent outward in the width direction and further protrudes outward in the width direction. The protruding portion is an input portion 72. A columnar boss 73 protruding outward in the width direction is formed in the middle of the main body 70.

8). Contact Mechanism As shown in FIG. 3 to FIG. 5A, each developing pressing boss 62 is attached to each second side plate 24 of the drawer 4 while the developing unit 8 is being attached to the drawer 4. An operating contact mechanism 75 is provided. The contact mechanism 75 includes four pressing cams 76 and four pressing springs 77 (see FIG. 5A) that elastically press each pressing cam 76 against each developing pressing boss 62.

  As shown in FIG. 5A, the pressing cam 76 is formed in a substantially triangular plate shape in a side view. A second support shaft 39 that protrudes inward in the width direction of the second side plate 24 is inserted into one corner of the press cam 76, and the press cam 76 is supported by the second support shaft 39 so as to be swingable. . The pressing cam 76 is provided in a posture extending obliquely upward on the rear side from one corner portion supported by the support shaft 39. The pressing spring 77 is wound around the second support shaft 39, and one end thereof is locked on the flange portion 33 of the second side plate 24, and the other end is locked by the pressing cam 76. As a result, the front end portion of the pressing cam 76 is urged toward the lower rear side, and the developing unit 8 is in contact with the developing pressing boss 62 from the upper front side with the developing unit 8 mounted on the drawer 4. The pressing boss 62 is urged downward.

9. Mounting operation of developing unit to drawer As shown in FIG. 3, the developing unit 8 of each color is mounted between the left and right second side plates 24 from above. At this time, both end portions of the roller shaft 59 protruding from both side walls 55 of the developing frame 51 of the developing unit 8 are introduced into the developing unit guide portion 37 from above. Then, both end portions of the roller shaft 59 are guided by the developing unit guide portion 37, whereby the developing unit 8 moves downward.

  Then, as shown in FIG. 5A, when the developing unit 8 is guided to the developing unit holding unit 38 and the developing roller 7C comes into contact with the photosensitive drum 5, further pressing of the developing unit 8 is restricted, and the developing unit 8 is controlled. The roller 7C is positioned with respect to the photosensitive drum 5. At this time, the development pressing boss 62 of the developing unit 8 is formed between the pressing cam 76 and the connecting portion 71 of the moving member 61 when viewed from the left-right direction (the direction from the front side to the back side in FIG. 5A). Passing through, it goes under the pressing cam 76. Then, the developing pressing boss 62 is urged downward by the pressing spring 77 and the pressing cam 76. As a result, the developing unit 8 is pressed downward, the developing roller 7C comes into contact with the photosensitive drum 5, and the photosensitive drum 5 is further moved. It will be in the state to press. In this state, the boss 73 of the moving member 61 enters the contact groove 50 of the second side plate 24 (see FIG. 2) and is disposed at a position slightly spaced from the lower surface of the contact groove 50. .

  The position of the developing unit 8 shown in FIG. 5A, that is, the position where the developing roller 7C comes into contact with the photosensitive drum 5 is the “contact position”. As described above, in this embodiment, the developing roller 7C presses the photosensitive drum 5 at the “contact position”, but the developing roller 7C simply contacts the photosensitive drum 5 at the “contact position”. It may be. In this embodiment, the drawer 4 can be attached to and pulled out from the apparatus main body at the “contact position”. As will be described later, the position of the developing unit 8 shown in FIG. 5B, that is, the position where the developing roller 7C is separated from the photosensitive drum 5 is the “separated position”.

  As shown in FIG. 2, when each developing unit 8 is mounted on the drawer 4, each developing coupling 64 faces each developing coupling insertion hole 41. When the drawer 4 in such a state is mounted on the housing 2 and reaches the mounting position described above, the motor provided in the housing 2 (see FIG. 1) with respect to each developing coupling insertion hole 41. A drive transmission unit (not shown) for transmitting a driving force from (not shown) is inserted. Each drive transmission unit is coupled to each development coupling 64, whereby a rotational driving force is transmitted to the development roller 7C and the supply roller 7B (see FIG. 1) via each drive transmission unit and the development coupling 64. .

10. Positioning structure and mounting operation when the drawer is mounted on the apparatus main body As shown in FIG. 4, a pair of main body side plates 81 (the right main body side plate on the right side) are opposed to each other in the width direction in the housing 2. 81 is shown). A roller member 82 is rotatably supported at the front end portion of the main body side plate 81 so as to abut against the flange portion 33 of each second side plate 24 from below and to slidably guide the drawer 4 with respect to the inside of the housing 2. ing. In addition, one main body reference shaft 83 is installed between the rear end portions of the left and right main body side plates 81.

  When the drawer 4 is mounted on the apparatus main body, first, the rear end edge of the flange portion 33 of the second side plate 24 is set to the upper side with respect to the roller member 82 with the front cover 3 (see FIG. 1) opened. Abut. Thereafter, when the drawer 4 is inserted toward the back side in the housing 2, the flange 33 slides on the roller member 82, and the drawer 4 is guided to the back in the housing 2. At this time, each input unit 72 moves above each cam 96 of the linear cam 92 described later. When the roller member 82 comes into contact with the inclined surface 34 (see FIG. 2 and the like) provided on the front side of the flange portion 33, the drawer 4 moves downward as a whole, and then the notch portion 31 of the first side plate 23 is moved. It contacts the main body reference shaft 83 from above and from the front. Further, when the both ends of the support shaft 25 push the groove portion 130 provided at the front edge of the main body side plate 81 rearward and downward, further pushing of the drawer 4 is restricted. At this time, each input unit 72 moves downward so as to enter between each cam 96 described later. Thus, the mounting operation of the drawer 4 to the apparatus main body is completed.

  The operation of pulling out the drawer 4 from the apparatus main body is the reverse of the mounting operation described above. Here, even while the drawer 4 is being pulled out from the apparatus main body, the contact mechanism 75 holds the developing unit 8 at the contact position by the urging force of the pressing spring 77.

11. Separation Mechanism As shown in FIG. 4, a separation mechanism 91 is provided above the main body side plate 81 in the housing 2. The separation mechanism 91 operates in cooperation with the contact mechanism 75 in a state in which the drawer 4 is attached to the apparatus main body, and thereby a “contact position” (a position where each developing unit 8 comes into contact with each photosensitive drum 5) (see FIG. 5 (a)) and a “separation position” (a position shown in FIG. 5B) where each developing unit 8 is separated from each photosensitive drum 5. When the developing unit 8 is in the “contact position”, the process cartridge 7 is in a state where image formation is possible, that is, the first state of the present invention. On the other hand, when the developing unit 8 is in the “separated position”, the process cartridge 7 is in a state where image formation is impossible, that is, the second state of the present invention.

  The separation mechanism 91 includes a pair of rails 93, a pair of linear motion cams 92 held by the pair of rails 93, and a synchronous movement mechanism 94 for linearly moving the linear motion cams 92 synchronously. Have. As shown in FIGS. 4 and 7, each linear cam 92 is guided by each rail 93 and is linearly movable in the front-rear direction (the direction in which the process cartridges 7 are arranged). The linear cam 92 is an example of the displacement means of the present invention.

  Each rail 93 (only the right rail 93 is shown) is fixed to the main body side plate 81 on both sides in the left-right direction in the housing 2, and extends in the front-rear direction. It has the 1st collar part 100 extended toward the width direction inner side from an edge, and the 2nd collar part 101 extended toward the width direction inner side from the lower end edge of the rail main body 99. As shown in FIG. The second flange 101 is formed with a stopper 102 that extends further upward from the inner edge in the width direction. In the middle part in the front-rear direction of the stopper part 102, four concave parts 103 having a shape cut out from the upper end thereof are formed.

  At the rear end of the rail body 99 and the first flange 100, a notch 104 is formed by cutting out from the upper surface in a rectangular shape in a side view. A linear motion cam 92 is disposed on the second flange 101 with the cam 96 protruding inward in the width direction. The cam 96 is an example of the action part of the present invention.

  As shown in FIG. 6, the left and right linear cams 92 basically have the same shape but differently. However, an input rack gear portion 92A extending in the front-rear direction is integrally formed at the approximate center of the left side surface of the left linear cam 92.

  The linear cam 92 integrally includes a main body portion 95 that is an extended member extending from the foremost process cartridge 7 to the rearmost process cartridge 7 and four cams 96 that are arranged in the front-rear direction on the inner surface of the main body portion 95. Is prepared. Each cam 96 is provided so as to correspond to each input portion 72 protruding above the developing unit 8 for each color. A rearward end portion of the cam 96 is formed with a first inclined surface 97 that is inclined downward from the upper end edge toward the front side. Further, on the lower surface side of the cam 96, a second inclined surface 98 that is continuous with the first inclined surface 97 and extends horizontally toward the front is formed.

  The three rear cams (three cams 96 other than the foremost cam 96) are formed so that the intervals between adjacent cams 96 are equal. On the other hand, the foremost cam 96 is formed such that the interval between the adjacent cams 96 is larger than the interval between the three rear cams 96.

  The synchronous movement mechanism 94 includes a left rack gear portion 92B formed on an upper surface of a rear end portion of the left linear motion cam 92, a left pinion gear 110 meshing with the left rack gear portion 92B, and a rear end portion of the right linear motion cam 92. A right rack gear portion 92C formed on the upper surface, a right pinion gear 111 meshing with the right rack gear portion 92C, and a connecting shaft 112 for connecting the left pinion gear 110 and the right pinion gear 111 in a relatively non-rotatable manner.

  The left direct acting cam 92 has a guide portion 92D that protrudes further rearward by the left rack gear portion 92B. The lower surface of the guide portion 92D is inclined upward toward the rear. An upper end portion 400B of an interlocking mechanism 400 described later is brought into contact with or separated from the lower surface of the guide portion 92D.

12 Driving Means As shown in FIG. 6, driving means 90 for driving the separation mechanism 91 is provided between the left outer wall (not shown) of the housing 2 and the left main body side plate (not shown). It has been.

  The drive means 90 is an electric motor having a drive transmission gear 90A that meshes with the input rack gear portion 92A. When the drawer 4 is mounted on the apparatus main body, the driving unit 90 is rotated by being controlled by the control unit at the time of color image formation or monochrome image formation, so that the input rack gear unit 92A is connected via the drive transmission gear 90A. The driving force is transmitted to As a result, the left direct acting cam 92 formed integrally with the input rack gear portion 92A linearly moves forward or backward. Then, the displacement is transmitted by the synchronous movement mechanism 94 to the right translation cam 92, so that the right translation cam 92 also moves linearly forward or backward.

13. Reading Unit As shown in FIGS. 1, 8, and 9, the reading unit 300 is a pair of left and right optical sensors provided in the housing 2 so as to face the conveyance belt 11 </ b> C from the rear. Although not shown, the reading unit 300 receives light reflected from the conveyor belt 11C adjacent to the light emitting unit that irradiates light from obliquely below the portion of the conveyor belt 11C that is wound around the driving roller 11A. And a light receiving portion.

  As shown in FIG. 8, the reading unit 300 is accommodated in a resin bracket 309 that is elongated in the width direction. Both ends of the resin bracket 309 are fixed to the left and right main body side plates 81. The reading unit 300 has a detection surface 301 that faces the conveyor belt 11C. The detection surface 301 is made of a transparent resin plate member that is elongated in the width direction, is fitted into the opening of the resin bracket 309, and is inclined so that the upper end edge is located rearward with respect to the lower end edge. With such a configuration, the detection surface 301 prevents toner and dust from reaching the light emitting unit and the light receiving unit while transmitting light from the light emitting unit constituting the reading unit 300 to the light receiving unit.

  As shown in FIG. 9, when forming a color image, the control unit first circulates the conveyor belt 11C and controls each process cartridge 7 before forming an image on the sheet to control the left and right sides on the sheet conveying surface 11D. A pair of detection patterns 305C, 305M, 305Y, and 305K are formed. Detection patterns 305C to 305K shown in FIG. 9 are examples of various detection patterns. The detection patterns 305 </ b> C to 305 </ b> K pass above the reading unit 300 by circulation of the transport belt 11 </ b> C. Then, the control unit causes the reading unit 300 to read the detection patterns 305C to 305K and output them as electric signals. Thereafter, the detection patterns 305C to 305K are removed from the conveyor belt 11C by a belt cleaner (not shown) disposed below the conveyor belt 11C.

14 Detection Unit As shown in FIG. 1, the detection unit 390 is provided in the housing 2 and is connected to the reading unit 300 by a signal wiring 390A. The detection unit 390 is provided inside a control unit that controls the image forming unit 10 and the like.

  The detection unit 390 performs an arithmetic process on the electrical signal output from the reading unit 300 and compares, for example, the pulse interval of the electrical signal with a threshold value. Then, the detection unit 390 determines whether or not the images formed by the process cartridges 7 are misaligned and whether they are misaligned when no correction related to the image forming operation is performed after the misalignment detection operation. If so, it is detected how much misalignment occurs. When the detection result is transmitted to the control unit, the control unit performs a correction process on the image forming operation of each process cartridge 7 so as to eliminate the positional deviation between the images.

14 Shutter Member As shown in FIGS. 8A and 8B, the shutter member 350 has a substantially “L” cross-sectional shape and is elongated in the width direction, and both ends of the shield 351. It is the resin-made member which has the side wall part 352 extended below from.

  A support hole 352A is formed below each side wall portion 352. The shutter member 350 is supported by fitting bosses (not shown) projecting outward from the left and right side walls of the resin bracket 309 into the support hole 352A, and swings about the swing axis X1 along the left and right direction. It is possible to move.

  In the left side wall portion 352, an engagement shaft portion 352B that is formed in a cylindrical shape and protrudes to the left is formed behind and above the support hole 352A.

  The shield 351 extends from the left reading unit 300 to the right reading unit 300 above the resin bracket 309. As shown in FIGS. 10 to 12, a brush-like cleaning member 360 is attached to the lower surface of the plate-like portion extending forward of the shielding portion 351. The cleaning member 360 may be, for example, a scraping blade made of a soft material, a nonwoven fabric, or the like.

  As shown in FIG. 8A, the shutter member 350 is displaced to the closed position covering the detection surface 301 by swinging forward around the swing axis X1. At this time, the cleaning member 360 moves to the lower end edge side of the detection surface 301 while being in contact with the detection surface 301 to remove the dirt attached to the detection surface 301.

  On the other hand, as shown in FIG. 8B, the shutter member 350 is displaced to the open position where the detection surface 301 is opened by swinging backward about the swing axis X1. Also at this time, the cleaning member 360 moves to the upper edge side of the detection surface 301 while being in contact with the detection surface 301 to remove the dirt adhering to the detection surface 301, and then further to a position where the detection surface 301 is not covered. Moving.

15. Interlocking Mechanism As shown in FIGS. 1, 6, and 9, the interlocking mechanism 400 is disposed on the outer side in the width direction of the conveyor belt 11C and behind the driving roller 11A.

  As shown in FIGS. 8A and 8B, the interlocking mechanism 400 is a rod-like body that is elongated in the vertical direction, and a support hole 400C is formed in an intermediate portion in the vertical direction. The interlocking mechanism 400 is supported by a left main body side plate (not shown) through a support hole 400C and can swing around a swing axis X2 along the left-right direction.

  The lower end portion 400A of the interlocking mechanism 400 has a fork shape that is divided into two forks, has a groove, and the engaging shaft portion 352B of the side wall portion 352 is inserted therein. The engagement shaft portion 352B is supported so as to be rotatable and slidable in the groove of the lower end portion 400A. On the other hand, as shown in FIG. 6, the upper end portion 400B of the interlocking mechanism 400 extends to the rear end portion 92D of the left direct acting cam 92, and has a rounded shape.

  As shown in FIGS. 8A and 8B, a coil spring 409 that urges the upper end 400B to move forward is provided between the interlocking mechanism 400 and the left main body side plate (not shown). Is provided.

  As shown in FIG. 10, when the linear motion cam 92 moves forward and the guide portion 92D is in the second range E2, the guide portion 92D is separated forward from the upper end portion 400B of the interlocking mechanism 400. . In this case, as shown in FIGS. 8B and 10, the upper end portion 400B is urged by the coil spring 409, swings forward around the swing axis X2, and stops against a stopper (not shown). It has become. Accordingly, the lower end portion 400A of the interlocking mechanism 400 swings rearward around the swing axis X2 and pushes the engagement shaft portion 352B rearward. As a result, the shutter member 350 swings rearward around the swing axis X1 and is displaced to the open position. FIG. 10 corresponds to FIG. 4 and shows a case (color mode) in which all process cartridges are in the first state in which an image can be formed. That is, as shown in FIG. 10, when the guide portion 92D is in the second range E2, the color mode is set, and the shutter member 350 opens the detection surface 301.

  When the linear motion cam 92 in the state shown in FIG. 10 moves rearward and the guide portion 92D is displaced from the second range E2 to the first range E1 as shown in FIG. 11, the guide portion 92D has an upper end portion 400B. Abut. Then, as shown in FIGS. 8A and 11, the upper end portion 400B is pushed by the guide portion 92D and swings backward around the swing axis X2 while resisting the biasing force of the coil spring 409. In this state, the lower surface of the guide portion 92D comes into sliding contact. Accordingly, the lower end portion 400A swings forward around the swing axis X2 and pushes the engagement shaft portion 352B forward. As a result, the shutter member 350 swings forward around the swing axis X1 and is displaced to the closed position. 11 corresponds to FIG. 4 similarly to FIG. 10 and shows a case where all the process cartridges are in the first state (color mode). That is, as shown in FIG. 11, when the guide portion 92 </ b> D is in the first range E <b> 1, the color mode is set, but the shutter member 350 covers the detection surface 301.

  When the linear motion cam 92 in the state shown in FIG. 11 further moves rearward and the guide portion 92D is displaced rearward from the first range E1 as shown in FIG. 12, FIG. 6, FIG. As shown in FIG. 12, the upper end portion 400B is in sliding contact with the lower surface of the guide portion 92D and maintains a state where it swings backward about the swing axis X2. In this case, the shutter member 350 remains displaced to the closed position. FIG. 12 corresponds to FIG. 7 and shows a case where the black process cartridge is in the first state where image formation is possible and the process cartridges other than black are in the second state where image formation is impossible (monochrome mode). Show. That is, as shown in FIG. 11, when the guide portion 92 </ b> D is behind the first range E <b> 1, the monochrome mode is set and the shutter member 350 covers the detection surface 301.

16. Operation of Linear Motion Cam, Shutter Member, and Interlocking Mechanism During Color Image Formation During color image formation, the control unit controls the driving means 90 to move the linear motion cam 92 forward as shown in FIG. The guide 92D is in the second range E2. Then, as shown in FIG. 4, the first inclined surface 97 of each cam 96 and the input portion 72 of the moving member 61 disposed behind each of the cams 96 face each other in a non-contact state with an interval in the front-rear direction. . Between the first inclined surface 97 of the foremost cam 96 and the input part 72 of the moving member 61 arranged behind the first inclined surface 97, the first inclined surface 97 of the rear three cams 96 and the respective rear sides thereof are arranged. An interval larger than the interval between the moving member 61 and the input unit 72 is formed. At this time, each pressing cam 76 abuts against the development pressing boss 62 of each developing unit 8 from above and presses each developing pressing boss 62 downward. As a result, each developing unit 8 is brought into a contact position, and as shown in FIG. 10, all process cartridges 7 are in a first state in which an image can be formed (color mode).

  Further, in conjunction with the movement of the linear motion cam 92, the upper end portion 400B moves away from the guide portion 92D, and as described above, the interlock mechanism 400 displaces the shutter member 350 to the open position, and the cleaning member 360 The detection surface 301 is cleaned. Then, while the control unit circulates the conveyance belt 11C, the detection patterns 305C to 305K are formed in each process cartridge 7, and the reading unit 300 and the detection unit 390 are controlled to perform the positional deviation detection operation. Then, if necessary, correction processing for eliminating the positional deviation is performed on each process cartridge 7.

  Thus, when the positional deviation detection work is completed, the control unit stops the reading unit 300 and the detection unit 390. Then, the control unit controls the driving means 90 to move the linear cam 92 in the state shown in FIG. 10 rearward, and as shown in FIG. The state is in one range E1. Then, the upper end portion 400B is guided by the guide portion 92D and swings backward, so that the interlocking mechanism 400 displaces the shutter member 350 to the closed position as described above, and the cleaning member 360 cleans the detection surface 301. . Thereafter, the control unit causes the paper feeding unit 220, the image forming unit 10, the transport unit 11, and the fixing device 13 to cooperate to form a color image on the paper transported along the transport path P.

17. Operation of Linear Motion Cam, Shutter Member, and Interlocking Mechanism During Monochrome Image Formation Since a misregistration detection operation by the reading unit 300 and the detection unit 390 is not necessary during monochrome image formation, the control unit causes the reading unit 300 and the detection unit 390 to Leave it stopped. Then, the control unit controls the driving means 90 to move the linear cam 92 in the state shown in FIG. 11 to the rear, and as shown in FIG. 12, the guide portion 92D is located behind the first range E1. A state is assumed. Then, as shown in FIG. 7, the first inclined surfaces 97 of the three rear cams 96 abut against the input portions 72 of the three rear moving members 61 disposed below each of the rear cams, 72 is pressed downward toward the rear side.

  By this pressing, as shown in FIG. 5B, the three rear moving members 61 are rotated downward on the rear side with the support shaft 60 as a fulcrum. During the rotation of the moving member 61, the boss 73 of each moving member 61 comes into contact with the lower surface of the contact groove 50 of the second side plate 24 from above.

  When the linear movement cam 92 moves rearward and the input portions 72 of the three rear moving members 61 move forward relative to the first inclined surface 97 of the cam 96, the input portion 72 further moves to the rear side. Move down. If it does so, the connection part 71 will be lifted up front side by using the boss | hub 73 as a fulcrum. For this reason, a pressing force toward the front upper side is applied to the three rear developing units 8 via the support shaft 60 that rotatably supports the connecting portion 71, and the pressing force applied from the pressing cam 76 is applied. In contrast, the developing unit 8 is lifted upward.

  When the linear movement cam 92 further moves rearward and the input portions 72 of the moving member 61 come into contact with the second inclined surfaces 98 of the three rear cams 96, the three rear development units 8 are separated from each other. The developing roller 7 </ b> C is greatly separated from the photosensitive drum 5. As a result, the process cartridges 7 other than black are in a second state where image formation is impossible. On the other hand, the development pressing boss 62 of the developing unit 8 corresponding to the foremost black remains pressed by the pressing cam 76. As a result, the black process cartridge 7 maintains the first state (monochrome mode).

  In conjunction with such movement of the linear cam 92, as shown in FIG. 12, the upper end portion 400B is guided by the guide portion 92D and swings backward, so that it is interlocked as described above. The mechanism 400 keeps the shutter member 350 displaced to the closed position. Thereafter, the control unit causes the paper feeding unit 220, the image forming unit 10, the transport unit 11, and the fixing device 13 to cooperate to form a monochrome image on the paper transported along the transport path P.

<Effect>
According to the printer 1 of the embodiment, the interlocking mechanism 400 displaces the shutter member 350 in conjunction with the displacement of the linear cam 92 that switches each process cartridge 7 to the first state or the second state. At this time, the interlocking mechanism 400 displaces the shutter member 350 to the closed position when the reading unit 300 does not operate, and displaces the shutter member 350 to the open position when the reading unit 300 operates. For this reason, since the shutter member 350 covers the detection surface 301 during a period when the detection unit 390 is not used, it is possible to reliably prevent the contamination of toner, dust, and the like from adhering to the detection surface 301. As a result, the printer 1 can reliably maintain the detection accuracy of the reading unit 300, so that it is possible to reliably prevent misalignment between the images during color image formation.

  Further, since the shutter member 350 is opened and closed by the linear cam 92 and the interlocking mechanism 400, it is not necessary to provide an opening / closing switching mechanism dedicated to the shutter member 350, so that the apparatus configuration can be simplified.

  Therefore, the printer 1 according to the embodiment can reliably prevent the positional deviation between the images at the time of forming the color image while realizing the simplification of the apparatus configuration.

  Further, in this printer 1, the developing unit 8 is brought into contact with or separated from the photosensitive drum 5 using the linear motion cam 92 having the main body 95 and the cam 96 and the moving member 61, so that the apparatus configuration is simplified. Can be realized more reliably.

  Further, in this printer 1, since the interlocking mechanism 400 reliably displaces the shutter member 350 to the open position during color image formation, which is the case where the reading unit 300 operates, detection of misalignment between the images during color image formation. Work can be performed reliably.

  Further, in the printer 1, after the linear motion cam 92 is displaced to the second range E2 and the shutter member 350 is displaced to the open position, the reading unit 300 and the detection unit 390 perform the positional deviation detection work, When the linear cam 92 is displaced to the first range E1 to displace the shutter member 350 to the closed position, the detection surface 301 is formed during the color image formation after the completion of the misalignment detection operation, which is the case where the reading unit 300 does not operate. It is possible to reliably prevent dirt from adhering to the surface. As a result, it becomes easier to maintain the detection accuracy of the reading unit 300, and the positional deviation between the images can be more reliably prevented.

  Further, in the printer 1, when the monochrome image is formed, which is a case where the reading unit 300 does not operate, the interlocking mechanism 400 displaces the shutter member 350 to the closed position, so that it is possible to reliably prevent the dirt from adhering to the detection surface 301. . As a result, it becomes easier to maintain the detection accuracy of the reading unit 300, and the positional deviation between the images can be more reliably prevented.

  Further, in this printer 1, when the shutter member 350 is displaced, the cleaning member 360 comes into contact with the detection surface 301 of the reading unit 300, so that dirt such as toner and dust attached to the detection surface 301 can be removed. It becomes easy to maintain the detection surface 301 in a clean state. As a result, the detection accuracy of the reading unit 300 can be more easily maintained, and the positional deviation between the images can be prevented more reliably.

  Further, in this printer 1, since the interlocking mechanism 400 is located on the outer side in the width direction of the transport belt 11C, interference between the interlocking mechanism 400 and other members disposed on the transport belt 11C is less likely to occur. As a result, the interlocking mechanism 400 can be operated reliably.

  In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and can be appropriately modified and applied without departing from the spirit of the present invention.

  For example, the process cartridge 7 may be switched to the second state by separating the photosensitive drum 5 and the developing unit 8 together with respect to the transport belt 11C.

  In the embodiment, the direct tandem type laser pre-interpreter has been described as an example, but the present invention can also be applied to an intermediate transfer type image forming apparatus.

  The present invention can be used for an image forming apparatus, a multifunction machine, and the like.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus (printer), P ... Conveyance path, 11C ... Endless belt (conveyance belt)
DESCRIPTION OF SYMBOLS 5 ... Image carrier (photosensitive drum), 8 ... Development unit, 7 ... Process cartridge 92 ... Displacement means (linear motion cam), 95 ... Main part, 96 ... Action part (cam)
301: Detection surface, 305C, 305M, 305Y, 305K ... Detection pattern 300 ... Reading means, 390 ... Detection means, 350 ... Shutter member, 400 ... Interlocking mechanism 61 ... Actuated part (moving member), 360 ... Cleaning member, E1 ... 1st range, E2 ... 2nd range

Claims (7)

An apparatus main body provided with a conveyance path for conveying a recording medium;
An endless belt that circulates in contact with the recording medium transported along the transport path;
An image carrier on which an electrostatic latent image is formed, and a developing unit that supplies toner to the image carrier and visualizes the electrostatic latent image, and circulates above the endless belt. A plurality of process cartridges that are arranged along a direction and sequentially form a plurality of color images on the recording medium or the endless belt;
An image forming apparatus comprising: a displacement unit that switches the process cartridge between a first state in which image formation is possible and a second state in which image formation is impossible by relative displacement with respect to each process cartridge;
A reading unit having a detection surface facing the endless belt, and reading a detection pattern formed on the endless belt by the process cartridges to detect a positional shift between the images through the detection surface; ,
Detection means for detecting a positional deviation between the images formed by the process cartridges based on a reading result of the reading means;
A shutter member provided between the endless belt and the detection surface and capable of being displaced to a closed position covering the detection surface and an open position opening the detection surface;
In conjunction with the relative displacement of the displacement means with respect to each process cartridge, the shutter member is displaced to the closed position when the reading means does not operate, while the shutter member is moved when the reading means operates. An interlocking mechanism for displacing to the open position ,
The displacement means can be displaced between a first range and a second range in a state where a plurality of the process cartridges are switched to the first state, and in the first range, the shutter member is displaced to the closed position. are allowed, in the second range, the image forming apparatus characterized that you have configured the shutter member to displace said open position. The interlocking mechanism is configured to displace the shutter member to the open position when the displacement means switches a plurality of the process cartridges to the first state for color image formation. Image forming apparatus. The displacing means is provided at a position corresponding to each process cartridge in the main body and relatively displaced along the arrangement direction of the process cartridges, and a plurality of actions that are displaced integrally with the main body. And when the main body is relatively displaced in the forward direction or the reverse direction with respect to each process cartridge, the working unit contacts the developing unit with the image carrier in the corresponding process cartridge. by spaced apart, corresponding said process the image forming apparatus of cartridge according to claim 1 or 2, wherein is configured to switch to the first state or the second state. The main body is an extending member extending long from the process cartridge on one end side in the arrangement direction to the process cartridge on the other end side,
Each of the action portions is a cam protruding from the main body portion toward the corresponding process cartridge,
Each of the process cartridges is connected to the developing unit, and an actuated part that receives the action of the corresponding actuating part is formed.
The image forming apparatus according to claim 3 , wherein the developing unit is configured to be brought into contact with or separated from the image carrier by guiding the acting portion to the acting portion. The interlocking mechanism moves the shutter member to the closed position when the displacement means switches one of the process cartridges to the second state while the one process cartridge is in the first state for monochrome image formation. The image forming apparatus according to any one of claims 1 to 4 , wherein the image forming apparatus is configured to be displaced to a predetermined distance. The shutter member, the closed position or the image forming apparatus according to any one of the open position the contact with the detection surface to claim 1 and a cleaning member for cleaning when displaced 5. The interlocking mechanism includes an image forming apparatus according to any one of the endless claim belts are disposed outward in the width direction of 1 to 6.

Images